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Supplementary Table 1. Linkage disequilibrium patterns of the tag-SNPs used for genotyping the 6q23.3 locus. Supplementary Table 2. Cytogenetic and molecular information on AML patients used for functional studies (n=12). Supplementary Table 3. French-American-British (FAB) classification35 and molecular information on AML patients used to determine miR-3662's abundance (n=8). Supplementary Table 4. Canonical pathway analysis of the miR-3662-associated gene expression signature. Supplementary Figure 1. Transcription factor binding according to the transcription factor chip data from ENCODE. Supplementary Figure 2. Electrophoretic mobility shift assay comparing the binding affinity of the alleles of rs66650371 and rs9483788. Supplementary Figure 3. Endogenous miR-3662 expression levels of hematopoietic progenitor (HP) cells during differentiation, total bone marrow aspirate of three non-leukemic donors (total BM 1-3), different populations of differentiated peripheral blood cells, and three AML cell lines. Supplementary Figure 4. Top panel, Macroscopic pictures of the spleens of three mice of the scramble and miR-3662-infected groups (organs harvested post-mortem). All mice had a massive splenomegaly compared to the un-injected, sacrificed control mouse. Bottom panel, images of spleen histologies (40x enlargement). Slides were stained for CD45 to proof MV4-11 origin of the leukemia. Supplementary Figure 5. Endogenous abundance of miR-3662 and IKBKB in patient samples and cell lines. Supplementary Figure 6. Comparison of the relative miR-3662 abundance of AML patient blasts and AML cell lines before (black) and after (red) forced miR-3662 expression with the lentiviral expression construct.

Supplementary Methods, Supplementary References Supplementary Table S1: Inherited regions of homozygosity in >1% of 1,798 non-leukemic individuals Supplementary Table S2: Acquired uniparental disomies detected in 425 cytogenetically normal AML patients Supplementary Table S3. Associations between recurrent UPDs with pretreatment patient characteristics for patients with cytogenetically normal acute myeloid leukemia Supplementary Table S5. Variant allele fraction of gene mutations that co-occurred with UPDs Supplementary Table S6. Allelic ratio of FLT3 internal tandem duplications that co-occurred with UPDs Supplementary Table S7: Copy number gains and losses in 425 patients with cytogenetically normal acute myeloid leukemia

Purpose:Uniparental disomy (UPD) is a way cancer cells duplicate a mutated gene, causing loss of heterozygosity (LOH). Patients with cytogenetically normal acute myeloid leukemia (CN-AML) do not have microscopically detectable chromosome abnormalities, but can harbor UPDs. We examined the prognostic significance of UPDs and frequency of LOH in patients with CN-AML.Experimental Design: We examined the frequency and prognostic significance of UPDs in a set of 425 adult patients with de novo CN-AML who were previously sequenced for 81 genes typically mutated in cancer. Associations of UPDs with outcome were analyzed in the 315 patients with CN-AML younger than 60 years.Results:We detected 127 UPDs in 109 patients. Most UPDs were large and typically encompassed all or most of the affected chromosome arm. The most common UPDs occurred on chromosome arms 13q (7.5% of patients), 6p (2.8%), and 11p (2.8%). Many UPDs significantly cooccurred with mutations in genes they encompassed, including 13q UPD with FLT3-internal tandem duplication (FLT3-ITD; P < 0.001), and 11p UPD with WT1 mutations (P = 0.02). Among patients younger than 60 years, UPD of 11p was associated with longer overall survival (OS) and 13q UPD with shorter disease-free survival (DFS) and OS. In multivariable models that accounted for known prognostic markers, including FLT3-ITD and WT1 mutations, UPD of 13q maintained association with shorter DFS, and UPD of 11p maintained association with longer OS.Conclusions:LOH mediated by UPD is a recurrent feature of CN-AML. Detection of UPDs of 13q and 11p might be useful for genetic risk stratification of patients with CN-AML.

Mutations detected in 425 CN-AML patients

Purpose: Aberrant DNA methylation, now recognized as a contributing factor to neoplasia, often shows definitive gene/sequence preferences unique to specific cancer types. Correspondingly, distinct combinations of methylated loci can function as biomarkers for numerous clinical correlates of ovarian and other cancers.Experimental Design: We used a microarray approach to identify methylated loci prognostic for reduced progression-free survival (PFS) in advanced ovarian cancer patients. Two data set classification algorithms, Significance Analysis of Microarray and Prediction Analysis of Microarray, successfully identified 220 candidate PFS-discriminatory methylated loci. Of those, 112 were found capable of predicting PFS with 95% accuracy, by Prediction Analysis of Microarray, using an independent set of 40 advanced ovarian tumors (from 20 short-PFS and 20 long-PFS patients, respectively). Additionally, we showed the use of these predictive loci using two bioinformatics machine-learning algorithms, Support Vector Machine and Multilayer Perceptron.Conclusion: In this report, we show that highly prognostic DNA methylation biomarkers can be successfully identified and characterized, using previously unused, rigorous classifying algorithms. Such ovarian cancer biomarkers represent a promising approach for the assessment and management of this devastating disease.

Supplementary Table 1 from Origins and Prevalence of the American Founder Mutation of MSH2

Supplementary Table 2 from A Susceptibility Locus for Papillary Thyroid Carcinoma on Chromosome 8q24

Supplementary Table 2 from Xenoestrogen-Induced Epigenetic Repression of microRNA-9-3 in Breast Epithelial Cells

Supplementary Figure 1 from A Susceptibility Locus for Papillary Thyroid Carcinoma on Chromosome 8q24

Supplementary Figures 1-6, Tables 1-15, Methods from Epigenetic Silencing Mediated through Activated PI3K/AKT Signaling in Breast Cancer

Supplementary Figure 2 from A Susceptibility Locus for Papillary Thyroid Carcinoma on Chromosome 8q24

Supplementary Table 1 from A Susceptibility Locus for Papillary Thyroid Carcinoma on Chromosome 8q24

Supplementary Figure 1 from Origins and Prevalence of the American Founder Mutation of MSH2

Supplementary Table 1 from Xenoestrogen-Induced Epigenetic Repression of microRNA-9-3 in Breast Epithelial Cells

The interplay between histone modifications and promoter hypermethylation provides a causative explanation for epigenetic gene silencing in cancer. Less is known about the upstream initiators that direct this process. Here, we report that the Cystatin M (CST6) tumor suppressor gene is concurrently down-regulated with other loci in breast epithelial cells cocultured with cancer-associated fibroblasts (CAF). Promoter hypermethylation of CST6 is associated with aberrant AKT1 activation in epithelial cells, as well as the disabled INNP4B regulator resulting from the suppression by CAFs. Repressive chromatin, marked by trimethyl-H3K27 and dimethyl-H3K9, and de novo DNA methylation is established at the promoter. The findings suggest that microenvironmental stimuli are triggers in this epigenetic cascade, leading to the long-term silencing of CST6 in breast tumors. Our present findings implicate a causal mechanism defining how tumor stromal fibroblasts support neoplastic progression by manipulating the epigenome of mammary epithelial cells. The result also highlights the importance of direct cell-cell contact between epithelial cells and the surrounding fibroblasts that confer this epigenetic perturbation. Because this two-way interaction is anticipated, the described coculture system can be used to determine the effect of epithelial factors on fibroblasts in future studies. [Cancer Res 2008;68(24):10257–66]

Supplementary Table 2 from Origins and Prevalence of the American Founder Mutation of MSH2

Supplementary Table 3 from A Susceptibility Locus for Papillary Thyroid Carcinoma on Chromosome 8q24

Supplementary Methods, Figures 1-5, Tables 1-5 from Breast Cancer–Associated Fibroblasts Confer AKT1-Mediated Epigenetic Silencing of Cystatin M in Epithelial Cells

Large germline deletions within the mismatch repair gene MSH2 account for a significant proportion (up to 20%) of all deleterious mutations of this gene which are associated with Lynch syndrome. An exons 1 to 6 deletion of MSH2, originally reported in nine families, has been associated with a founding event within the United States, which genealogic studies had previously dated to 1727, and the number of present day carriers was estimated to be 18,981. Here, we report the development of a robust multiplex PCR which has assisted in the detection of 32 new families who carry the MSH2 American Founder Mutation (AFM). By offering testing to family members, 126 carriers of the AFM have been identified. Extensive genealogic studies have connected 27 of the 41 AFM families into seven extended pedigrees. These extended families have been traced back to around the 18th century without any evidence of further convergence between them. Characterization of the genomic sequence flanking the deletion and the identification of a common disease haplotype of between 0.6 and 2.3 Mb in all probands provides evidence for a common ancestor between these extended families. The DMLE+2.2 software predicts an age of ∼500 years (95% confidence interval, 425–625) for this mutation. Taken together, these data are suggestive of an earlier founding event than was first thought, which likely occurred in a European or a Native American population. The consequences of this finding would be that the AFM is significantly more frequent in the United States than was previously predicted. [Cancer Res 2008;68(7):2145–53]

Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer. The molecular characteristics of histologically normal appearing tissue adjacent to the tumor (NAT) from PTC patients are not well characterized. The aim of this study was to characterize the global gene expression profile of NAT and compare it with those of normal and tumor thyroid tissues. We performed total RNA sequencing with fresh frozen thyroid tissues from a cohort of three categories of samples including NAT, normal thyroid (N), and PTC tumor (T). Transcriptome analysis shows that NAT presents a unique gene expression profile, which was not associated with sex or the presence of lymphocytic thyroiditis. Among the differentially expressed genes (DEGs) of NAT vs N, 256 coding genes and 5 noncoding genes have been reported as cancer genes involved in cell proliferation, apoptosis, and/or tumorigenesis. Bioinformatics analysis with Ingenuity Pathway Analysis software revealed that “Cancer, Organismal Injury and Abnormalities, Cellular Response to Therapeutics, and Cellular Movement” were major dysregulated pathways in the NAT tissues. This study provides improved insight into the complexity of gene expression changes in the thyroid glands of patients with PTC.

Progressive metastasis is the proximate cause of cancer-related mortality for the majority of patients with solid tumors. Identifying both drivers, and gatekeepers of late stage progression (metastasis progression suppressors; MPS) is crucial to improve biomarkers and treatments. We previously identified Regulator of Calcineurin 1.4 (RCAN1.4) as a MPS gene in thyroid cancer that functions in part through overexpression of the cap-n-collar transcription factor NFE2L3 (NRF3). However, the mechanisms for RCAN1.4 loss in thyroid cancer, and whether or not this is reversible, had not be addressed. Because the RCAN 1.4 promoter contains CG rich regions reported to be hypermethyalated in other tissues, we hypothesized that RCAN 1.4 downregulation in thyroid cancer was similarly regulated. Studies were performed in both cell lines and de-identified human papillary thyroid cancer (PTC) tumor and normal tissue pairs from our Endocrine Neoplasia Repository tumor bank. Five thyroid cancer cell lines (TPC1, FTC133, BCPAP, C643, and 8505C) with different genetic drivers were selected based on low expression of RCAN 1.4. To determine if lines display methylation-regulated expression of RCAN 1.4, cells were treated with 1-10uM decitabine, a DNA methyl transferase inhibitor. In all cell lines, RCAN1.4 mRNA and protein levels increased with decitabine treatment, consistent with hypermethylation. Analysis of the literature and in silico analysis of the RCAN 1.4 gene identified CG rich regions as putative methylation targets in the proximal promoter and in intron 1. Using two different methods; 1) isolation of MseI-digestion DNA fragments using CpG MethylQuest beads followed by qPCR and 2) methylation-specific PCR (MSP) of bisulfite-modified DNA, hypermethylation of the intron 1 CG rich region was identified. There was no evidence of hypermethylation of the CG rich region of the proximal promoter. Methylation of the two regions also was assessed on 18 pairs PTC and adjacent normal tissues. Similar to the cell lines, hypermethylation was identified at intron 1 of RCAN 1.4 in PTC versus normal tissues. QRT-PCR results confirmed lower levels of RCAN1-4 mRNA in the PTC vs normal tissue. These samples also demonstrated increased NRF3 expression versus normal tissue. Taken together, these data demonstrate that RCAN 1.4 is downregulated in thyroid cancer cells and human PTCs by hypermethylation of CG rich regions in intron 1 and that this effect is reversible using demethylating agents. Presentation: Saturday, June 11, 2022 11:45 a.m. - 12:00 p.m.

BackgroundPapillary thyroid carcinoma (PTC) demonstrates high heritability and a low somatic mutation burden relative to other cancers. Therefore, the genetic risk predisposing to PTC is likely due to a combination of low penetrance variants. A recent genome-wide association study revealed the association of PTC with a missense variant, rs6793295, at 3q26 in a gene called Leucine Repeat Rich Containing 34 (LRRC34).MethodsWe report the mechanisms of PTC risk at 3q26 using a combination of overexpression, mass spectroscopy, knockdown, transcriptome profiling, migration assays and genetic analysis.ResultsWe observed differential binding of wild-type and missense LRRC34 to RANBP1. Overexpression of missense LRRC34 reduced RanGTP levels and increased apoptosis. We also identified a second linkage disequilibrium (LD) block upstream of LRRC34 containing regulatory variants with allele-specific expression. Transcriptome profiling of LRRC34 knockdown cells showed changes in genes involved with cellular movement. LRRC34 knockdown reduced the migration of thyroid cancer cell lines. Lastly, we assessed the relative contribution of PTC risk from each locus using haplotype analysis.ConclusionsOur study demonstrates two separate mechanisms, one in G protein signalling and the other in transcriptional control, dictating PTC risk at 3q26 using both biochemical and genetic techniques.

Background: Our genome sequencing analysis revealed a frameshift mutation in the shelterin gene TINF2 in a large family with individuals affected with papillary thyroid carcinoma (PTC) and melanoma. Here, we further characterized the mutation and screened for coding variants in the 6 shelterin genes in 24 families. Methods: Sanger sequencing was performed to screen for the TINF2 mutation in the key family. Quantitative reverse transcription-polymerase chain reaction (PCR) was used for TINF2 gene expression analysis. Exogenous expression and co-immunoprecipitation techniques were used for assessing TINF2 binding to TERF1. Relative telomere length (RTL) was quantified in DNAs from lymphocytes by using quantitative real-time PCR. Whole exome sequencing (WES) was performed in seven families with individuals affected with PTC and other cancer types. Screening for DNA variants in shelterin genes was performed by using whole genome sequencing data from 17 families and WES data from 7 further families. Results: The TINF2 mutation (TINF2 p.Trp198fs) showed complete co-segregation with PTC and melanoma in the key family. The mutation is not reported in databases and not identified in 23 other families we screened. The expression of TINF2 was borderline reduced in individuals with the mutation. The truncated TINF2 protein showed abolished binding to TERF1. The RTL in the individuals with the mutation was significantly longer when compared with those without the mutation from the same family as well as compared with 62 healthy controls. Among the 24 families, we identified 3 missense and 1 synonymous variant(s) in 2 shelterin genes (TINF2 and ACD). Conclusions: The rare frameshift mutation in the TINF2 gene and the associated longer telomere length suggest that dysregulated telomeres could be a mechanism predisposing to PTC and melanoma. DNA coding variants in shelterin genes are rare. Further studies are required to evaluate the roles of variants in shelterin genes in thyroid cancer and melanoma.

The original version of this article contained an error in the results, in the second paragraph of the subsection entitled “Fine-mapping for potentially causal variants among TSH loci”, in which effect sizes for two variants were incorrectly reported.

Purpose:Uniparental disomy (UPD) is a way cancer cells duplicate a mutated gene, causing loss of heterozygosity (LOH). Patients with cytogenetically normal acute myeloid leukemia (CN-AML) do not have microscopically detectable chromosome abnormalities, but can harbor UPDs. We examined the prognostic significance of UPDs and frequency of LOH in patients with CN-AML.Experimental Design: We examined the frequency and prognostic significance of UPDs in a set of 425 adult patients with de novo CN-AML who were previously sequenced for 81 genes typically mutated in cancer. Associations of UPDs with outcome were analyzed in the 315 patients with CN-AML younger than 60 years.Results:We detected 127 UPDs in 109 patients. Most UPDs were large and typically encompassed all or most of the affected chromosome arm. The most common UPDs occurred on chromosome arms 13q (7.5% of patients), 6p (2.8%), and 11p (2.8%). Many UPDs significantly cooccurred with mutations in genes they encompassed, including 13q UPD with FLT3-internal tandem duplication (FLT3-ITD; P < 0.001), and 11p UPD with WT1 mutations (P = 0.02). Among patients younger than 60 years, UPD of 11p was associated with longer overall survival (OS) and 13q UPD with shorter disease-free survival (DFS) and OS. In multivariable models that accounted for known prognostic markers, including FLT3-ITD and WT1 mutations, UPD of 13q maintained association with shorter DFS, and UPD of 11p maintained association with longer OS.Conclusions:LOH mediated by UPD is a recurrent feature of CN-AML. Detection of UPDs of 13q and 11p might be useful for genetic risk stratification of patients with CN-AML.

Background: Thyroid cancer patients with radioiodine-refractory (RAI-R) disease, resulting from insufficient RAI delivery and/or RAI resistance, have increased mortality and limited treatment options. To date, studies have largely focused on tumor mutations associated with different stages of disease, which could provide prognostic value for RAI-R disease. It was hypothesized that germline variants contributing to intrinsic differences in iodine metabolism, tumor microenvironment, and/or immune surveillance are associated with RAI-R disease. Methods: Whole-genome genotyping data analysis was performed on 1145 Caucasian (CAU) patients, 244 of whom were RAI-R, and 55 African American (AA) patients, nine of whom were RAI-R. Germline-variant association studies were conducted using candidate genes involved in iodine metabolism or DNA-damage repair, as well as genome-wide association analysis. Initial data indicated several notable variants in a small number of patients (n = 7), who were later determined to be AA patients of >80% African ancestry (n = 37). This led to the study focusing on germline single nucleotide polymorphisms uniquely associated with RAI-R AA patients. Sanger sequencing was performed to validate risk alleles and identify the incidence of the common somatic mutations BRAF(V600E), NRAS(Q61R), and HRAS(Q61R) in AA patients whose primary tumor samples were available (28/55). Results: TG, BRCA1, and NSMCE2 haplotypes were identified as being uniquely associated with RAI-R AA patients of >80% African ancestry. All patients with the TG haplotype (n = 4) had a biochemical incomplete response to RAI therapy. Patients with the NSMCE2 haplotype (n = 4) were diagnosed at a young age (13, 17, 17, and 26 years old) with distant metastatic disease at initial diagnosis. The BRCA1 haplotype co-occurred in three out of four patients with the NSMCE2 haplotype. The incidence of BRAF(V600E) appears lower in papillary thyroid carcinomas from AA patients of >80% African ancestry (3/14; 21%) than in AA patients of

BackgroundPatients with colorectal cancer (CRC) with mismatch repair-deficient (dMMR) tumours without MLH1 methylation or germline MMR pathogenic variants (PV) were previously thought to have Lynch syndrome (LS). It is now appreciated that they can have double somatic (DS) MMR PVs. We explored the clinical characteristics between patients with DS tumours and LS in two population-based cohorts.MethodsWe included patients with CRC from Ohio 2013–2016 and Iceland 2000–2009. All had microsatellite instability testing and/or immunohistochemistry (IHC) of MMR proteins, and MLH1 methylation testing when indicated. Germline next-generation sequencing was performed for all with dMMR tumours; tumour sequencing followed for patients with unexplained dMMR. Clinical characteristics of DS patients and patients with LS were compared.ResultsOf the 232 and 51 patients with non-methylated dMMR tumours in the Ohio and Iceland cohorts, respectively, 57.8% (n=134) and 45.1% (n=23) had LS, 32.8% (n=76) and 31.4% (n=16) had DS PVs, 6% (n=14) and 9.8% (n=5) were unexplained and 4.3% (n=10) and 13.7% (n=7) had incorrect IHC. Age of diagnosis for DS patients was older than patients with LS (p=3.73×10−4) in the two cohorts. Patients with LS were more likely to meet Amsterdam II criteria (OR=15.81, p=8.47×10−6) and have multiple LS-associated tumours (OR=6.67, p=3.31×10−5). Absence of MLH1/PMS2 was predictive of DS PVs; isolated MSH6 and PMS2 absence was predictive of LS in both cohorts.ConclusionsIndividuals with LS are 15× more likely to meet Amsterdam II criteria and >5× more likely to have multiple cancers as compared with those with DS tumours. Furthermore, isolated loss of MSH6 or PMS2 protein predicts LS.

Background We studied a large family with 22 individuals affected with autosomal dominant hereditary spherocytosis (HS). Methods Genome‐wide linkage, whole‐genome sequencing (WGS), Sanger sequencing, RT‐PCR, and ToPO TA cloning analyses were performed. Results We revealed a heterozygous G>A transition in the 14q23 locus, at position +1 of the intron 8 donor splice site of the spectrin beta, erythrocytic (SPTB) gene. This splice variant (SPTB c.1064+1G>A) was confirmed by Sanger sequencing and showed complete co‐segregation with HS in the family. Further RT‐PCR reactions and sequencing analysis indicated that the variant leads to the exclusion of exon 8 and subsequent frameshift in exon 9 and a premature stop codon in SPTB. Translation of the altered allele would lead to a truncation with a loss of all spectrin repeat domains in SPTB protein. Conclusion This variant is novel and has not been found in any databases. We propose that this splice variant explains the spherocytosis phenotype observed in this large family., We studied a large family with 22 individuals affected with autosomal dominant hereditary spherocytosis (HS). Genome‐wide linkage and whole‐genome sequencing analyses revealed a heterozygous G>A transition in the 14q23 locus, at position +1 of the intron 8 donor splice site of the spectrin beta, erythrocytic (SPTB) gene.

Incidence of differentiated thyroid carcinoma (DTC) varies considerably between ethnic groups, with particularly high incidence rates in Pacific Islanders. Here, we conducted a genome-wide association study (GWAS) involving 1,554 cases/1,973 controls of European ancestry and 301 cases/348 controls of Oceanian ancestry from the EPITHYR consortium. Our results confirmed the association with the known DTC susceptibility loci at 2q35, 8p12, 9q22.33 and 14q13.3 in the European ancestry population and suggested two novel signals at 1p31.3 (rs334729) and 16q23.2 (rs16950982), which were associated with TSH levels in previous GWAS. We additionally replicated an association with 5p15.33 reported previously in Chinese and European populations. Except at 1p31.3, all associations were in the same direction in the population of Oceanian ancestry. The frequency of risk alleles at 2q35, 5p15.33 and 16q23.2 were significantly higher in Oceanians than in Europeans and may explain part of the highest DTC incidence observed in Oceanians.Competing Interest StatementThe authors have declared no competing interest.Funding StatementINCA (grant number 9533) and ARC (grant number PGA120150202302), Ligue Nationale Contre le Cancer, Agence Nationale pour la Recherche (ANR), the Direction Generale de la Sante, the Agence Francaise de Securite Sanitaire de l alimentation, de lenvironnement et du travail (ANSES), CHILDTHYR EEC program, and the Fondation de France. JG and CX were the recipient of a PhD fellowship from Region Ile-de-France.Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:All participants provided informed consent and each study was approved by their governing ethics committee.All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.YesThe data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions. (Less)

Papillary thyroid carcinoma (PTC) is the most common histotype of thyroid carcinoma. The heritability of PTC is high compared to other cancers, but its underlying causes are unknown. A recent genome-wide association study revealed the association of a variant at the 5q22 locus, rs73227498, with PTC predisposition. We report that rs17134155, a variant in high linkage disequilibrium with rs73227498, is located in an enhancer region downstream of coding transcripts of EPB41L4A. Rs17134155 showed significant enhancer activity in luciferase assays, and haplotypes containing the protective allele of this variant conferred a significantly lower risk of PTC. While the index SNP, rs73227498, acted as a significant cis-eQTL for expression of EPB41L4A, rs17134155 was a significant cis-sQTL for the alternative splicing of a non-coding transcript of EPB41L4A, called EPB41L4A-203. We also performed knockdown of EPB41L4A followed by microarray analysis. Some of the top differentially-expressed genes were represented among regulators of the WNT/β-catenin signaling pathway. Our results indicate that an enhancer region at 5q22 regulates the expression and splicing of EPB41L4A transcripts. We also provide evidence that EPB41L4A expression is involved in regulating growth and differentiation pathways, suggesting that decreased expression of EPB41L4A is a mechanism in the predisposition to PTC.

The first two genome wide association studies (GWAS) of papillary thyroid carcinoma (PTC) detected five variants associated with PTC. Two of them (rs944289 and rs116909374) are located at 14q13 making that locus an important target of research into the genetic predisposition to PTC. We aimed at uncovering other variants at 14q13 associated with PTC independently from the GWAS variants. We performed next generation sequencing of the 14q13 region and analyzed the allele frequencies of single nucleotide polymorphisms (SNPs) in n = 90 PTC cases vs. n = 379 EUR controls from the 1,000 Genome Project. The variants associated with PTC were validated in an Ohio cohort of n = 1,216 PTC cases and n = 1,416 controls. Next, we analyzed the association between SNPs and expression of nearby genes and clinical parameters. We showed that rs368187 was associated with PTC (OR = 1.31, p = 2.20 × 10-6 ). Rs1632250, Rs1863347 and rs1755787 showed association with classical PTC (cPTC) (n = 891; OR = 1.24, 2.22 × 10-3 , OR = 1.31, p = 2.15 × 10-4 and OR = 1.24, p = 2.06 × 10-3 , respectively) while variant rs28397092 showed association with follicular variant (n = 243; OR = 1.51, p = 1.36 × 10-3 ). Rs1863347 was associated with suppression of PTCSC3 in unaffected thyroid tissue (p = 0.026). Rs1632250, rs1863347 and rs1755787 showed association with multifocality (OR = 1.85, p = 0.001, OR = 1.98, p = 0.001 and OR = 1.76, p = 0.003 respectively) and N stage (OR = 1.79, p = 0.014, OR = 1.73, p = 0.023 and OR = 1.81, p = 0.013, respectively) in microPTC (n = 328) while rs368187 was associated with M stage (OR = 0.56, p = 0.034) in cPTC. Our results disclose multiple variants associated with PTC and clinical features in the 14q13 superlocus. We suggest that translational genotype/phenotype studies should take into account not only somatic mutations but also germline variants.

To identify and characterize the functional variants, regulatory gene networks, and potential binding targets of SMAD3 in the 15q22 thyroid cancer risk locus. We performed linkage disequilibrium (LD) and haplotype analyses to fine map the 15q22 locus. Luciferase reporter assays were applied to evaluate the regulatory effects of the candidate variants. Knockdown by small interfering RNA, microarray analysis, chromatin immunoprecipitation (ChIP) and quantitative real-time polymerase chain reaction assays were performed to reveal the regulatory gene network and identify its binding targets. We report a 25.6-kb haplotype within SMAD3 containing numerous single-nucleotide polymorphisms (SNPs) in high LD. SNPs rs17293632 and rs4562997 were identified as functional variants of SMAD3 by luciferase assays within the LD region. These variants regulate SMAD3 transcription in an allele-specific manner through enhancer elements in introns of SMAD3. Knockdown of SMAD3 in thyroid cancer cell lines revealed its regulatory gene network including two upregulated genes, SPRY4 and SPRY4-IT1. Sequence analysis and ChIP assays validated the actual binding of SMAD3 protein to multiple SMAD binding element sites in the region upstream of SPRY4. Our data provide a functional annotation of the 15q22 thyroid cancer risk locus.

Background: Our genome sequencing analysis revealed a frameshift mutation in the shelterin gene TINF2 in a large family with individuals affected with papillary thyroid carcinoma (PTC) and melanoma. Here, we further characterized the mutation and screened for coding variants in the 6 shelterin genes in 24 families. Methods: Sanger sequencing was performed to screen for the TINF2 mutation in the key family. Quantitative reverse transcription-polymerase chain reaction (PCR) was used for TINF2 gene expression analysis. Exogenous expression and co-immunoprecipitation techniques were used for assessing TINF2 binding to TERF1. Relative telomere length (RTL) was quantified in DNAs from lymphocytes by using quantitative real-time PCR. Whole exome sequencing (WES) was performed in seven families with individuals affected with PTC and other cancer types. Screening for DNA variants in shelterin genes was performed by using whole genome sequencing data from 17 families and WES data from 7 further families. Results: The TINF2 mutation (TINF2 p.Trp198fs) showed complete co-segregation with PTC and melanoma in the key family. The mutation is not reported in databases and not identified in 23 other families we screened. The expression of TINF2 was borderline reduced in individuals with the mutation. The truncated TINF2 protein showed abolished binding to TERF1. The RTL in the individuals with the mutation was significantly longer when compared with those without the mutation from the same family as well as compared with 62 healthy controls. Among the 24 families, we identified 3 missense and 1 synonymous variant(s) in 2 shelterin genes (TINF2 and ACD). Conclusions: The rare frameshift mutation in the TINF2 gene and the associated longer telomere length suggest that dysregulated telomeres could be a mechanism predisposing to PTC and melanoma. DNA coding variants in shelterin genes are rare. Further studies are required to evaluate the roles of variants in shelterin genes in thyroid cancer and melanoma.

Genome-wide association studies (GWASs) have identified at least 10 single-nucleotide polymorphisms (SNPs) associated with papillary thyroid cancer (PTC) risk. Most of these SNPs are common variants with small to moderate effect sizes. Here we assessed the combined genetic effects of these variants on PTC risk by using summarized GWAS results to build polygenic risk score (PRS) models in three PTC study groups from Ohio (1,544 patients and 1,593 controls), Iceland (723 patients and 129,556 controls), and the United Kingdom (534 patients and 407,945 controls). A PRS based on the 10 established PTC SNPs showed a stronger predictive power compared with the clinical factors model, with a minimum increase of area under the receiver-operating curve of 5.4 percentage points ( P ≤ 1.0 × 10 −9 ). Adding an extended PRS based on 592,475 common variants did not significantly improve the prediction power compared with the 10-SNP model, suggesting that most of the remaining undiscovered genetic risk in thyroid cancer is due to rare, moderate- to high-penetrance variants rather than to common low-penetrance variants. Based on the 10-SNP PRS, individuals in the top decile group of PRSs have a close to sevenfold greater risk (95% CI, 5.4–8.8) compared with the bottom decile group. In conclusion, PRSs based on a small number of common germline variants emphasize the importance of heritable low-penetrance markers in PTC.

Publsiher's version (útgefin grein), Thyroid stimulating hormone (TSH) is critical for normal development and metabolism. To better understand the genetic contribution to TSH levels, we conduct a GWAS meta-analysis at 22.4 million genetic markers in up to 119,715 individuals and identify 74 genome-wide significant loci for TSH, of which 28 are previously unreported. Functional experiments show that the thyroglobulin protein-altering variants P118L and G67S impact thyroglobulin secretion. Phenome-wide association analysis in the UK Biobank demonstrates the pleiotropic effects of TSH-associated variants and a polygenic score for higher TSH levels is associated with a reduced risk of thyroid cancer in the UK Biobank and three other independent studies. Two-sample Mendelian randomization using TSH index variants as instrumental variables suggests a protective effect of higher TSH levels (indicating lower thyroid function) on risk of thyroid cancer and goiter. Our findings highlight the pleiotropic effects of TSH-associated variants on thyroid function and growth of malignant and benign thyroid tumors., We acknowledge the University of Michigan Precision Health Initiative and Medical School Central Biorepository for providing biospecimen storage, management, processing, and distribution services, and the Center for Statistical Genetics in the Department of Biostatistics at the School of Public Health for genotype data curation, imputation, and management in support of this research (for MGI cohort). The biochemical work at the University of Michigan was done with funding from NIH R01 DK-40344. This research has been conducted using the UK Biobank Resource under application number 24460. The HUNT Study is a collaboration between the HUNT Research Centre (Faculty of Medicine and Health Sciences, NTNU, Norwegian University of Science and Technology), Nord-Trøndelag County Council, Central Norway Regional Health Authority, and the Norwegian Institute of Public Health. The genotyping in HUNT was financed by the National Institutes of Health; University of Michigan; the Research Council of Norway; the Liaison Committee for Education, Research and Innovation in Central Norway; and the Joint Research Committee between St Olav’s Hospital and the Faculty of Medicine and Health Sciences, NTNU. We thank Sean Caron for web development for data sharing. Support for this research was provided by NIH grant DK062370 (M.B.). Ohio State Cohort was supported by NIH P50CA168505 SPORE (M.D.R. and A.d.l.C.). Support for the HUNT and MGI analysis was additionally provided by R35HL135824 (C.J.W.) and R01HL109946 (C.J.W.). W.Z. was supported by the National Human Genome Research Institute of the National Institutes of Health under award number T32HG010464. G.D.S., B.B., H.R. and E.B.H. work in the Medical Research Council Integrative Epidemiology Unit at the University of Bristol MC_UU_00011/1.

Papillary thyroid carcinoma (PTC) demonstrates high heritability and a low somatic mutation burden relative to other cancers. Therefore, the genetic risk predisposing to PTC is likely due to a combination of low penetrance variants. A recent genome-wide association study revealed the association of PTC with a missense variant, rs6793295, at 3q26 in a gene called Leucine Repeat Rich Containing 34 (We report the mechanisms of PTC risk at 3q26 using a combination of overexpression, mass spectroscopy, knockdown, transcriptome profiling, migration assays and genetic analysis.We observed differential binding of wild-type and missense LRRC34 to RANBP1. Overexpression of missense LRRC34 reduced RanGTP levels and increased apoptosis. We also identified a second linkage disequilibrium (LD) block upstream ofOur study demonstrates two separate mechanisms, one in G protein signalling and the other in transcriptional control, dictating PTC risk at 3q26 using both biochemical and genetic techniques.

Background: Familial non-medullary thyroid cancer (NMTC) accounts for a relatively small proportion of thyroid cancer cases, but it displays strong genetic predisposition. So far, only a few NMTC susceptible genes and low-penetrance variants contributing to NMTC have been described. This study aimed to identify rare germline variants that may predispose individuals to NMTC by sequencing a cohort of 17 NMTC families. Methods: Whole-genome sequencing and genome-wide linkage analysis were performed in 17 NMTC families. MendelScan and BasePlayer were applied to screen germline variants followed by customized filtering. The remaining candidate variants were subsequently validated by Sanger sequencing. A panel of 277 known cancer predisposition genes was also screened in these families. Results: A total of 41 rare coding candidate variants in 40 genes identified by whole-genome sequencing are reported, including 24 missense, five frameshift, five splice change, and seven nonsense variants. Sanger sequencing confirmed all 41 rare variants and proved their co-segregation with NMTC in the extended pedigrees. In silico functional analysis of the candidate genes using Ingenuity Pathway Analysis showed that cancer was the top category of "Diseases and Disorders." Additionally, a targeted search displayed six variants in known cancer predisposition genes, including one frameshift variant and five missense variants. Conclusions: The data identify rare germline variants that may play important roles in NMTC predisposition. It is proposed that in future research including functional characterization, these variants and genes be considered primary candidates for thyroid cancer predisposition.

Long noncoding RNAs (lncRNAs) regulate pathological processes, yet their potential roles in papillary thyroid carcinoma (PTC) are poorly understood.To profile transcriptionally dysregulated lncRNAs in PTC and identify lncRNAs associated with clinicopathological characteristics.We performed RNA sequencing of 12 paired PTC tumors and matched noncancerous tissues and correlated the expression of lncRNAs with clinical parameters. The 2 most significantly dysregulated lncRNAs were studied in an Ohio PTC cohort (n = 109) and in PTC data (n = 497) from The Cancer Genome Atlas.A combination of laboratory-based studies and computational analysis using clinical data and samples and a publically available database.Correlation between expression values and clinical parameters.We identified 218 lncRNAs showing differential expression in PTC (fold change ≥ 2.0, P.01). Significant correlation was observed between the expression of 2 lncRNAs (XLOC_051122 and XLOC_006074) and 1) lymph node metastasis (N stage) and 2) BRAF(V600E) mutation. Among patients with wild-type BRAF, the expression of these 2 lncRNAs showed significantly higher levels in the patients with lymph node metastasis. In silico analysis of these lncRNAs pinpointed cell movement and cellular growth and proliferation as targeted functions.Comprehensive expression screening identified 2 novel lncRNAs associated with risk factors of adverse prognosis in PTC patients. These lncRNAs may be novel players in PTC carcinogenesis.

Chromosomal aberrations and multiple genome-wide association studies (GWAS) have established a major hematopoietic quantitative trait locus in chromosome 6q23.3. The locus comprises an active enhancer region, in which some of the associated SNPs alter transcription factor binding. We now identify miR-3662 as a new functional driver contributing to the associated phenotypes. The GWAS SNPs are strongly associated with higher miR-3662 expression. Genome editing of rs66650371, a three-base-pair deletion, suggests a functional link between the SNP genotype and the abundance of miR-3662. Increasing miR-3662′s abundance increases colony formation in hematopoietic progenitor cells, particularly the erythroid lineage. In contrast, miR-3662 is not expressed in acute myeloid leukemia cells, and its overexpression has potent antileukemic effects in vitro and in vivo. Mechanistically, miR-3662 directly targets NF-κB–mediated transcription. Thus, miR-3662 is a new player of the hematopoietic 6q23.3 locus. Significance: The characterization of miR-3662 has identified a new actor in the prominent hematopoietic quantitative trait locus in chromosome 6q23.3. The mechanistic insights into miR-3662′s function may reveal novel or only partially known pathways for normal and malignant hematopoietic cell proliferation. Cancer Discov; 6(9); 1036–51. ©2016 AACR. This article is highlighted in the In This Issue feature, p. 932

Duchenne muscular dystrophy (DMD) is a neuromuscular disorder causing progressive muscle degeneration. Although cardiomyopathy is a leading mortality cause in DMD patients, the mechanisms underlying heart failure are not well understood. Previously, we showed that NF-κB exacerbates DMD skeletal muscle pathology by promoting inflammation and impairing new muscle growth. Here, we show that NF-κB is activated in murine dystrophic (mdx) hearts, and that cardiomyocyte ablation of NF-κB rescues cardiac function. This physiological improvement is associated with a signature of upregulated calcium genes, coinciding with global enrichment of permissive H3K27 acetylation chromatin marks and depletion of the transcriptional repressors CCCTC-binding factor, SIN3 transcription regulator family member A, and histone deacetylase 1. In this respect, in DMD hearts, NF-κB acts differently from its established role as a transcriptional activator, instead promoting global changes in the chromatin landscape to regulate calcium genes and cardiac function., The molecular mechanisms leading to heart failure in patients with Duchenne muscular dystrophy are unclear. Here the authors show that NF-κB is activated in the heart of dystrophin-deficient mice and that its ablation rescues cardiac function through chromatin remodeling and activation of gene expression.

We previously showed that a long noncoding RNA gene, PTCSC3, located close to the variant rs944289 that predisposes to papillary thyroid carcinoma (PTC) might target the S100A4 gene.The aim was to investigate the impact of PTCSC3 on S100A4 expression and its role in cancer development.S100A4 abundance was analyzed by quantitative PCR (qPCR) in unaffected and tumor tissue from n = 73 PTC patients. The expression of PTCSC3 and S100A4 was studied in BCPAP and TPC-1 cell lines with forced expression of PTCSC3 by qPCR. Expression of S100A4 target genes (VEGF and MMP-9) was studied in the BCPAP cell line with forced expression of PTCSC3 by qPCR, reverse transcriptase PCR, and Western blot. The impact of PTCSC3 on BCPAP motility and invasiveness was analyzed by the Transwell and Matrigel assays, respectively.This was a laboratory-based study using cells from clinical samples and thyroid cancer cell lines.We aimed to find evidence for a link between the expression of PTCSC3 and thyroid carcinogenesis.Expression data from PTC cell lines pinpointed S100A4 as the most significantly downregulated gene in the presence of PTCSC3. S100A4 was upregulated in tumor tissue (P = 9.33 × 10(-7)) while PTCSC3 was strongly downregulated (P = 2.2 × 10(-16)). S100A4 transcription was moderately correlated with PTCSC3 expression in unaffected thyroid tissue (r = 0.429, P = .0001), and strongly in unaffected tissue of patients with the risk allele of rs944289 (r = 0.685, P = 7.88 × 10(-5)). S100A4, VEGF, and MMP-9 were suppressed in the presence of PTCSC3 (P = .0051, P = .0090, and P =.0037, respectively). PTC cells expressing PTCSC3 showed reduction in motility and invasiveness (P = 4.52 × 10(-5) and P = 1.0 × 10(-4), respectively).PTCSC3 downregulates S100A4, leading to a reduction in cell motility and invasiveness. We propose that PTCSC3 impacts PTC predisposition and carcinogenesis through the S100A4 pathway.

The [A] allele of SNP rs965513 in 9q22 has been consistently shown to be highly associated with increased papillary thyroid cancer (PTC) risk with an odds ratio of ∼1.8 as determined by genome-wide association studies, yet the molecular mechanisms remain poorly understood. Previously, we noted that the expression of two genes in the region, forkhead box E1 (FOXE1) and PTC susceptibility candidate 2 (PTCSC2), is regulated by rs965513 in unaffected thyroid tissue, but the underlying mechanisms were not elucidated. Here, we fine-mapped the 9q22 region in PTC and controls and detected an ∼33-kb linkage disequilibrium block (containing the lead SNP rs965513) that significantly associates with PTC risk. Chromatin characteristics and regulatory element signatures in this block disclosed at least three regulatory elements functioning as enhancers. These enhancers harbor at least four SNPs (rs7864322, rs12352658, rs7847449, and rs10759944) that serve as functional variants. The variant genotypes are associated with differential enhancer activities and/or transcription factor binding activities. Using the chromosome conformation capture methodology, long-range looping interactions of these elements with the promoter region shared by FOXE1 and PTCSC2 in a human papillary thyroid carcinoma cell line (KTC-1) and unaffected thyroid tissue were found. Our results suggest that multiple variants coinherited with the lead SNP and located in long-range enhancers are involved in the transcriptional regulation of FOXE1 and PTCSC2 expression. These results explain the mechanism by which the risk allele of rs965513 predisposes to thyroid cancer.

Context: By genome-wide association studies, the risk allele [A] of SNP rs965513 predisposes strongly to papillary thyroid carcinoma (PTC). It is located in a gene-poor region of 9q22, some 60 kb from the FOXE1 gene. The underlying mechanisms remain to be discovered. Objective: Our objective was to identify novel transcripts in the 9q22 locus and correlate gene expression levels with the genotypes of rs965513. Design: We performed 3′ and 5′ rapid amplification of cDNA ends and RT-PCR to detect novel transcripts. One novel transcript was forcibly expressed in a cell line followed by gene expression array analysis. We genotyped rs965513 from PTC patients and measured gene expression levels by real-time RT-PCR in unaffected thyroid tissue and matched tumor. Setting: This was a laboratory-based study using cells from clinical tissue samples and a cancer cell line. Main Outcome Measures: We detected previously uncharacterized transcripts and evaluated the gene expression levels and the correlation with the risk allele of rs965513, age, gender, chronic lymphocyte thyroiditis (CLT), and TSH levels. Results: We found a novel long intergenic noncoding RNA gene and named it papillary thyroid cancer susceptibility candidate 2 (PTCSC2). Transcripts of PTCSC2 are down-regulated in PTC tumors. The risk allele [A] of rs965513 was significantly associated with low expression of unspliced PTCSC2, FOXE1, and TSHR in unaffected thyroid tissue. We also observed a significant association of age and CLT with PTCSC2 unspliced transcript levels. The correlation between the rs965513 genotype and the PTCSC2 unspliced transcript levels remained significant after adjusting for age, gender, and CLT. Forced expression of PTCSC2 in the BCPAP cell line affected the expression of a subset of noncoding and coding transcripts with enrichment of genes functionally involved in cell cycle and cancer. Conclusions: Our data suggest a role for PTCSC2, FOXE1, and TSHR in the predisposition to PTC.

Familial non-medullary thyroid cancer (FNMTC) is clinically defined as two or more first-degree relatives with NMTC and appears to follow an autosomal dominant inheritance pattern. Approximately 5–7% of NMTC is hereditary and affects multiple generations with a young age of onset. The primary aim of this study was to determine the age-specific penetrance of NMTC in individuals from a large family with FNMTC with a previously identified private mutation at 4q32, with a secondary aim to determine the penetrance for benign thyroid disease in this family. We present a large family with NMTC in which we had previously described a culpable mutation. Participants provided their personal medical history and family history. The germline 4q32 A > C mutation was detected in 34 of 68 tested individuals. Age-specific penetrance of thyroid cancer and benign thyroid disease was determined using the inverted Kaplan–Meier method of segregation analysis. Individuals who tested positive for the 4q32 mutation have a 68.9% (95% CI 46.5–88.7) risk of developing thyroid cancer by age 70 and a 65.3% (95% CI 46.0–83.8) risk of developing benign thyroid disease by age 70. The 4q32 A > C mutation significantly increases the risk to develop thyroid cancer but not benign thyroid disease in members of this family. The female:male sex ratio of 1.33 that we observed in affected mutation carriers differs greatly from the ratio of approximately 3:1 observed in PTC, supporting a central role of the mutation. Early thyroid surveillance with annual ultrasound is recommended to individuals testing positive for this private familial mutation.

Neuroblastoma rat sarcoma (RAS) viral oncogene homolog (NRAS), a small GTPase, is one of the most thoroughly studied oncogenes that controls cell growth, differentiation, and survival by facilitating signal transduction. Here, we identify four novel naturally occurring NRAS isoforms (isoforms 2-5) in addition to the canonical isoform (isoform 1). Expression analyses performed on a panel of several different human malignancies and matching normal tissue revealed distinct isoform expression patterns. Two of the novel isoforms were found in the nucleus and cytoplasm, whereas the others were exclusively cytoplasmic. The isoforms varied in their binding affinities to known downstream targets and differentially regulated the RAS signaling pathway. Strikingly, forced expression of isoform 5, which encodes only a 20-aa peptide, led to increased cell proliferation and to transformation by activation of known NRAS targets. These discoveries open new avenues in the study of NRAS.

Thyroid cancer is the 12th most common cancer in the USA. Four main types exist: the majority (85-90%) is papillary thyroid cancer (PTC). Familial form of PTC represents 5 to 15 % of all thyroid cancers. We have access to 155 PTC families including clinical data and biological samples. Our aim was to search for highly penetrant gene variants in 17 PTC families. Data from one of the families in which PTC is segregating in three generations are described here. Whole genome sequencing was performed in three family members affected by PTC. Sanger sequencing at germline DNA and RNA levels followed by TOPO cloning was used to study the effects of mutations. We found 4 different either novel or ultra-rare mutations in the ITGAD, AARS and PDPR genes on chromosome 16 (Table). All mutations segregated perfectly with PTC in family members (n=4) and were absent in unaffected members (n=3). We Sanger sequenced cDNA from two of the PTC patients and cloned the products into the pCR 2.1-® TOPO vector. Based on the cDNA sequencing and cloning results, all of the mutations will create a premature stop codon leading to a truncated protein. We will verify the effects of the mutations by protein analysis as well. In addition, structural variation analysis will be done to exclude large genomic rearrangements. The germline events leading to PTC are neither well known nor extensively researched. When occurring in families PTC regularly shows autosomal dominant inheritance with incomplete penetrance. Only a few of probable mutations have been reported. Nevertheless, our finding of the truncating mutations in 3 genes on chromosome 16 that are cosegregating with PTC in a 3-generation family is surprising. Even more so: is the localization of the three genes in one chromosome coincidental? Preliminary findings in some of the other 16 PTC families suggest that the occurrence of more than one truncating mutation is not a unique event. We look forward to answer the question whether combination of two or more mutant genes can be responsible for one disease segregating in families. Citation Format: Taina T. Nieminen, Daniel F. Comiskey, Yanqiang Wang, Sandya Liyanarachchi, Pamela Brock, Paivi Peltomaki, Huiling He, Albert de la Chapelle. Multiple rare germline variants in a thyroid cancer family [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4156.

Germline mutations in PMS2 are associated with Lynch syndrome (LS), the most common known cause of hereditary colorectal cancer. Mutation detection in PMS2 has been difficult due to the presence of several pseudogenes, but a custom-designed long-range PCR strategy now allows adequate mutation detection. Many mutations are unique. However, some mutations are observed repeatedly across individuals not known to be related due to the mutation being either recurrent, arising multiple times de novo at hot spots for mutations, or of founder origin, having occurred once in an ancestor. Previously, we observed 36 distinct mutations in a sample of 61 independently ascertained Caucasian probands of mixed European background with PMS2 mutations. Eleven of these mutations were detected in more than one individual not known to be related and of these, six were detected more than twice. These six mutations accounted for 31 (51%) ostensibly unrelated probands. Here, we performed genotyping and haplotype analysis in four mutations observed in multiple probands and found two (c.137G>T and exon 10 deletion) to be founder mutations and one (c.903G>T) a probable founder. One (c.1A>G) could not be evaluated for founder mutation status. We discuss possible explanations for the frequent occurrence of founder mutations in PMS2.